Luis Olivares-Quiroz, Autonomous University of Mexico City.
Proteins are long heteropolymer chains composed of units called aminoacids synthesized inside the cell by DNA translation and transcription in combination with the action of the ribosome and t-RNA chains. In order to perform a specific biological function, classical structure-form paradigm asserts that a protein has a single unique biologically active conformation which is called native state. The adquisition of an ordered structure from a disordered ensemble in which the number of potential conformations generates a vast and diverse conformational space poses several challenges and it is an excellent arena to be discussed into the light of statistical mechanics based models. To the present, very few analytical solvable models of this kind are known since most of the main stream has concentrated on numerical and computational approaches to treat the interacting Hamiltonian of the system protein-water. However, can we learn something about the basic mechanics behind order-disorder transitions in these systems from basic models?
In this talk I shall focus the attention to a particular class of statistical mechanics based coarse grained models both for homo and heteropolymer chains which admits a full analytical solution for the equilibrium partition function Z in the homopolymer case and can be readily generalized for the more general heteropolymer case. Results concerning the specific heat Cv, configurational entropy S and the existence of first- order phase transitions as functions of temperature and length of the chain will be discussed. Some brief remarks about open problems with this type of models as the so-called curve-inversion problem will be briefly sketched aand how the energy spectrum of the chain has indeed an influence on thermodynamic properties.